There are several problems associated with incorporating polymeric particles into a cement matrix. Firstly, polymer particles do not bind to a cement matrix, so although addition of these particles to the cement results in a lower Young's modulus, the tensile and compressive strengths of the system are also reduced. Secondly, polymer particles are typically low density, so when they are added to a cement system, in many cases weighting agents also need to be added to maintain the required density. It is sometimes difficult to stabilise systems that contain both lightweight polymeric particles and weighting agents. Thirdly, polymer particles are frequently hydrophobic and are thus sometimes difficult to mix during cement operations due to wettability and foaming issues.
A number of proposals have been made for using polymer particles in cements or other construction materials and oilfiled fluids. Examples include WO 06/085012, which describes the use of polymer particles coated with minerals for cementing applications (the minerals are present as anti-caking agents and are loosely attached at best to the surface of the polymer particles); U.S. Pat. No. 7,255,738, which discloses hydrophobic particles, coated with mineral fillers, used as lightweight roofing materials; WO07/074,330 which discloses a cement composition containing a particulate elastomer comprising a carboxy group, as well as methods of cementing and of enhancing the mechanical properties of a set cement composition and improved bonding; and WO04/07867 which discloses the addition of carboxylate monomers to acrylonitrile-butadiene elastomers to improve thermal stability. Ground car tyres (which themselves contain fillers such as carbon black and silica) have been also used in cement systems (U.S. Pat. No. 5,779,787 and U.S. Pat. No. 6,907,929). Deformable beads containing a solid core with a deformable outer layer have been disclosed for fracturing operations (U.S. Pat. No. 6,059,034). The use of lightweight polyamide particles for fracturing applications, with the option of having fillers to improve the properties, has also been described (US20070209795).
US20060258546 describes lightweight structured composites, containing particulates with tailored particle size distribution and a binder, and is in the field of proppants. The binder used is a phenol-formaldehyde or other thermoset resin. U.S. Pat. No. 6,406,789 and U.S. Pat. No. 6,632,527 describe a composite particle comprising filler particles distributed through a binder material. The main application is as a lightweight proppant. Methods to manufacture filled resin particles that could be used in cementing applications are also disclosed.